Various methods and systems are known in the art for protecting data in computer systems against disasters such as earthquakes, storms, floods, fires and terrorist attacks. Some solutions involve replicating (mirroring) the data in a primary and a secondary storage device. For example, EMC Corporation (Hopkinton, Mass.) offers a family of remote storage replication solutions called Symmetrix Remote Data Facility (SRDF) for disaster recovery and business continuity. The SRDF product family includes both synchronous and asynchronous solutions. As another example, IBM Corporation (Armonk, N.Y.) offers a number of business continuity solutions, including mirroring products.
PCT International Publication WO 2006/111958, whose disclosure is incorporated herein by reference, describes a method for data protection, which includes accepting data for storage from one or more data sources. The data is sent for storage in a primary storage device and in a secondary storage device. While awaiting an indication of successful storage of the data in the secondary storage device, a record associated with the data is temporarily stored in a disaster-proof storage unit adjacent to the primary storage device. When an event damaging at least some of the data in the primary storage device occurs, the data is reconstructed using the record stored in the disaster-proof storage unit and at least part of the data stored in the secondary storage device.